Limited Slip Differential with Electrohydraulic Clutch Actuator

Abstract

A power transfer device for a front wheel drive motor vehicle includes an input shaft driven by a power source, a second shaft driven by the first shaft through one of a plurality of speed gearsets, an output gearset driven by the second shaft and a differential assembly. The differential assembly includes an electronically controlled, hydraulically actuated, clutch operable to place the differential assembly in one of an open mode, a locked mode and a limited slip mode. A clutch actuator includes an electric motor coupled to a pump where the pump provides pressurized fluid to the clutch to operate the clutch in one of the locked and limited slip modes.

1 . A power transfer device for a front wheel drive motor vehicle having first and second driven front wheels, the power transfer device comprising:
 an input shaft adapted to be driven by a power source;   a second shaft driven by said first shaft through one of a plurality of speed gearsets;   an output gearset driven by said second shaft;   a differential assembly drivingly coupled to said output gearset, said differential assembly including a housing rotatably supported within said power transfer device, a pair of pinion gears rotatably supported by said housing and a pair of side gears, each side gear being in meshed engagement with said pinion gears;   first and second axle shafts being individually driven by said side gears;   an electronically controlled, hydraulically actuated clutch selectively drivingly interconnecting said first axle shaft and said differential housing to place said differential assembly in one of an open mode, a locked mode and a limited slip mode; and   a clutch actuator having an electric motor coupled to a pump, said pump providing pressurized fluid to said clutch to operate said differential assembly in one of said locked and limited slip modes.   
   
   
       2 . The power transfer device of  claim 1  further including a controller operable to determine impending slip of said first and second wheels and preemptively operating said clutch actuator to prevent first and second wheel slip. 
   
   
       3 . The power transfer device of  claim 2  wherein said controller determines impending slip based on information provided by a vehicle sensor. 
   
   
       4 . The power transfer device of  claim 3  wherein said vehicle sensor includes at least one of a vehicle throttle position sensor and a vehicle acceleration sensor. 
   
   
       5 . The power transfer device of  claim 1  wherein said first and second axle shafts rotate about an axis substantially parallel to and offset from an axis of rotation of said input shaft. 
   
   
       6 . The power transfer device of  claim 5  wherein said second shaft rotates about an axis substantially parallel to and offset from said input shaft axis. 
   
   
       7 . The power transfer device of  claim 1  further including a rotatable output member selectively driven by said input shaft and adapted to transfer torque to a set of driven rear wheels. 
   
   
       8 . The power transfer device of  claim 7  further including a mode clutch selectively operable to transfer torque to said output member. 
   
   
       9 . The power transfer device of  claim 1  wherein said output gearset includes a first gear driven by said second shaft and a second gear fixed to said differential housing. 
   
   
       10 . A power transfer device for a motor vehicle having first and second driven wheels, the power transfer device comprising:
 a rotatable input shaft;   a second shaft driven by said first shaft through one of a plurality of speed gearsets;   a differential assembly being driven by said second shaft, said differential assembly including a housing rotatably supported within said power transfer device, a pair of pinion gears supported for rotation within said housing and a pair of side gears, each side gear being in meshed engagement with said pinion gears;   first and second axle shafts being individually driven by said side gears;   a tubular transfer shaft fixed for rotation with said differential and at least partially encompassing said first axle shaft; and   a clutch selectively drivingly interconnecting said first axle shaft and said transfer shaft to place said differential assembly in one of an open mode, a locked mode and a limited slip mode.   
   
   
       11 . The power transfer device of  claim 10  further including a clutch actuator having an electric motor coupled to a pump, said pump providing pressurized fluid to said clutch to operate said differential assembly in one of said locked and limited slip modes. 
   
   
       12 . The power transfer device of  claim 11  wherein said clutch includes a drum fixed for rotation with said transfer shaft and a hub fixed for rotation with said first axle shaft. 
   
   
       13 . The power transfer device of  claim 12  further including a power transfer device housing having each of said input shaft, said second shaft, said differential assembly, said transfer shaft, said clutch and at least a portion of said first axle shaft positioned therein. 
   
   
       14 . The power transfer device of  claim 13  wherein said power transfer device housing contains lubricant and said clutch is a wet clutch positioned in contact with said lubricant. 
   
   
       15 . The power transfer device of  claim 11  wherein said electric motor has an output shaft rotating about an axis extending parallel to an axis of rotation of said first axle shaft. 
   
   
       16 . The power transfer device of  claim 11  wherein said clutch actuator includes a piston slidably positioned within a cavity to apply a force to said clutch. 
   
   
       17 . The power transfer device of  claim 11  further including a valve biased toward an open position to release pressurized fluid acting on said piston. 
   
   
       18 . The power transfer device of  claim 17  wherein said valve is moved to a closed position when said pump is actuated to trap pressurized fluid with said cavity and actuate said, clutch. 
   
   
       19 . The power transfer device of  claim 18  wherein deactivation of said pump causes said valve to move to said open position to rapidly deactivate said clutch. 
   
   
       20 . The power transfer device of  claim 10  further including a rotatable output member selectively driven by said input shaft and adapted to transfer torque to a set of driven rear wheels.